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United States Patent |
5,124,722
|
Moriyama
,   et al.
|
June 23, 1992
|
Ink jet recording method
Abstract
An ink jet recording method comprises
a recording head for discharging ink in response to a signal to be applied
thereto to perform the recording; and
drive unit for driving said recording head at each of a plurality of drive
frequency,
wherein at least one drive frequency is above a stable discharge speed
region and the discharge speed of ink at which ink is discharged in the
drive frequency being equal to the discharge speed at which ink is
discharged in the drive frequency of the stable discharge region.
Inventors:
|
Moriyama; Jiro (Yokohama, JP);
Takei; Masahiro (Yokohama, JP)
|
Assignee:
|
Canon Kabushiki Kaisha (Tokyo, JP)
|
Appl. No.:
|
701378 |
Filed:
|
May 13, 1991 |
Foreign Application Priority Data
| Jun 25, 1986[JP] | 61-149080 |
Current U.S. Class: |
347/9 |
Intern'l Class: |
B41J 002/04 |
Field of Search: |
346/1.1,140
|
References Cited
U.S. Patent Documents
4409596 | Oct., 1983 | Ishii | 346/1.
|
4475113 | Oct., 1984 | Lee | 346/1.
|
4523200 | Jun., 1985 | Howkins | 346/1.
|
4562445 | Dec., 1985 | Rich | 346/140.
|
4625221 | Nov., 1986 | Mizuno | 346/140.
|
4646106 | Feb., 1987 | Howkins | 346/1.
|
4743924 | May., 1988 | Scardovi | 346/140.
|
Primary Examiner: Hartary; Joseph W.
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper & Scinto
Parent Case Text
This application is a continuation of application Ser. No. 07/358,508 filed
May 30, 1989, which is a continuation of application Ser. No. 07/207,936
filed Jun 17, 1988, which is a continuation of application Ser. No.
07,065,390 filed Jun. 23, 1987, all now abandoned.
Claims
We claim:
1. A recording method comprising the steps of:
scanning an on-demand type ink jet recording head adjacent a recording
medium;
selecting at least one select frequency of electrical signals to be applied
to a discharge element of the recording head while the recording head is
scanning, the at least one select frequency being selected from a second
frequency range of first and second frequency ranges, the second frequency
range being greater than the first frequency range, wherein the discharge
speed of ink discharged in response to electrical signals at all
frequencies in the first frequency range is substantially constant, and
discharge speeds of ink discharged in response to electrical signals at
frequencies in the second frequency range vary as a function of frequency
of the electrical signal, and the at least one select frequency is
selected from the second frequency range such that the discharge speed of
ink discharge in response to electrical signals at the select frequency is
substantially equal to the speed of ink discharged in response to
electrical signals at all frequencies in the first frequency range;
applying the electrical signals to the discharge element of the recording
head, the frequency of the electrical signals being within the first
frequency range or being equal to the at least one select frequency from
the second frequency range; and
discharging ink at a substantially constant discharge speed onto the
recording medium in response to the applied electrical signals.
2. A recording method according to claim 1, wherein the discharge velocity
varies within .+-. 5% for all frequencies in the first frequency range and
for the second select frequencies of the second frequency range.
3. A recording method according to claim 1, further comprising the step of
capping the recording head at a location spaced from a recording area
where the recording head records on the recording medium.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet apparatus having a stable and
high discharge speed.
2. Related Background Art
In an ink jet printer which supplies an electrical signal to an
electro-mechanical transducer to discharge ink, an on-demand type ink jet
printer which discharges ink only when an input signal is applied has been
known.
A physical construction of major portions of such an ink jet printer is
shown in FIG. 5.
In FIG. 5 numeral 1 denotes a platen which is rotated by a line feed pulse
motor 7 to feed a record sheet, not shown. The presence or absence of the
record sheet is detected by a sheet sensor 9. Numeral 2 denotes an ink jet
recording head which has a plurality of ink discharge nozzles 30, is
provided on a carriage slidably arranged on a guide bar, not shown and is
movable along the platen 1 through a belt 14 by the drive of a D.C.
carriage motor 8. In order to detect the position of the recording head 2,
a linear encoder 12 and an encoder sensor 13 are provided, and in order to
detect a home position, a home position sensor 11 is provided. In order to
recover failure of ink discharge by the nozzles 30 of the recording head
2. an ink absorbing cap 3 which is movable by the drive of an auto-cap
motor 6 is provided and the position of the cap 3 is detected by a cap
sensor 10.
The control of the ink jet printer of such a construction is effected by a
known CPU 20 in a control system shown in FIG. 1. The CPU 20 effects the
following control operations in accordance with control inputs applied by
switches 21 on a console panel, not shown. It refers inputs from the
encoder sensor 13 and the home position sensor 11 to drive a carriage
motor 8 through a DC servo forward/backward switching circuit 22 and drive
a line feed motor 7 through a pulse motor drive circuit 23, and reads out
data from a record data memory D to get a drive frequency as shown in FIG.
4 and supplies it to a head driver 24 by which the recording head 2 is
driven. It also controls other units, not shown, in accordance with inputs
from other sensors.
When a print switch of the switches 21 is depressed, the record operation
is started. The presence of the record sheet is detected by the sheet
sensor 9 and the line feed motor 7 is driven by several steps so that the
platen 1 is rotated one revolution and the record sheet is set at a record
start position. Then, the carriage motor 8 is driven so that the recording
head 2 is reciprocally driven, and the line feed motor 7 is driven in
synchronism therewith to feed the record sheet line by line. During this
period, a drive signal is applied to the recording head 2 from the head
driver 24 in accordance with record data so that the recording head 2 is
driven and ink droplets d are discharged from the recording head 2 and
characters or images are recorded on the record sheets.
A relationship between a drive frequency f discharge of the recording head
2 of the ink and a discharge speed v of the ink is shown in FIG. 4.
In order to reduce a print time, the drive frequency f may be raised. But,
as seen from FIG. 4, the discharge speed v changes as the drive frequency
f rises.
As shown in FIG. 4, the characteristic of the drive frequency f has a
region I in which the discharge speed v does not change with the drive
frequency f and a region II in which the discharge speed v changes with
the drive frequency f. In order to attain a high quality of print, a drive
frequency f.sub.n which meets relationships of
##EQU1##
where f.sub.1 is a reference frequency equal to a maximum in the region I
and n is an integer equal to or larger than 2, is used.
Accordingly, when the drive frequency f is to be increased, the
characteristic of FIG. 4 is determined by a structure of the recording
head 2, a property of material of the ink and a head drive waveform.
Where the region II in which the discharge speed v is not constant is used,
a deviation l from the ink discharge point changes to l' when the ink
discharge speed v changes to v + .DELTA.v, and an ink deposit point is
deviated by
##EQU2##
where L is a distance between the record medium and the record head 2 and
V is a main scan speed of the record head 2.
Further, as the discharge speed v changes, a volume of ink droplet changes
and there is a correlation between those two.
For this reason, when the region in which the ink discharge speed v changes
with the drive frequency f is used, the quality of print is degraded.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an ink jet apparatus
which drives a head at a high drive frequency without degrading a print
quality so that a print time is shortened.
In accordance with the present invention, an ink jet apparatus having drive
means for discharging ink by driving the head at a plurality of drive
frequencies is provided in which the drive means has at least one drive
frequency which is beyond the region in which a stable discharge speed is
attained and at which a stable discharge speed is independently attained.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a block diagram of a printer control unit,
FIG. 2 shows a graph a drive frequency, a discharge speed and a deposit
point,
FIG. 3 shows an ink discharge speed and a deviation of the deposit point,
FIG. 4 shows a relationship between a drive frequency and an ink discharge
speed in a prior art apparatus, and
FIG. 5 shows a construction of major portions of an ink jet printer.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 2 shows a relationship between a drive frequency f and an ink
discharge speed v in an ink jet printer in accordance with the present
invention. A physical construction of major portions of the present ink
jet printer may be similar to that shown in FIG. 5, and a control circuit
therefor may be basically similar to that of FIG. 1, and explanation
thereof is omitted.
The structure of an apparatus and a control circuit used therein according
to the present invention may not be limited to a structure and a control
circuit shown in FIGS. 1 and 5, and therefore, another modified apparatus
capable of performing the functions described hereinafter according to the
present invention may be applied.
A maximum f.sub.1 of the drive frequency, which is a reference frequency,
is set to a frequency which is in a region II in which the discharge speed
v is variable and at which the discharge speed in the stable discharge
speed region I is attained. A drive frequency f.sub.n which is 1/n of the
reference frequency f.sub.1 (where n is an integer equal to or larger than
2) is set to a frequency in the region I. Thus, a frequency which is
approximately 1.2-2 times as high as the frequency in the prior art
apparatus may be used as the reference frequency f.sub.1 and the ink may
be discharged stably at a high speed.
At the drive frequencies f.sub.1, f.sub.2, . . . , no ink is discharged and
hence the ink discharge speed v need not be constant for the drive
frequency as it is in the region I and the drive frequencies f.sub.1,
f.sub.2, f.sub.3 . . . may be in the region II so long as they assure the
discharge speed in the region I.
The region I may be lower than a maximum frequency at which a variation of
the discharge speed v is within .+-. 5% for the drive frequency f, and the
region II may be higher than that frequency. At the drive frequencies
f.sub.1, f.sub.2, . . . f.sub.n, the variation of the discharge speed v
should meet the above condition (.+-. 5%). To this end, the structure of
the record head property of material of the ink and head drive waveform
are properly selected.
In accordance with the present invention, the drive frequency may be raised
without degrading the print quality so that the print time of the ink jet
apparatus is significantly shortened.
The apparatus according to the present invention can be also applied to an
ink jet recording method in which the discharge speed of a liquid droplets
depends on the driving frequency to be applied to driving elements, for
example a method using a piezo-electric elements as an energy generating
member (as shown in U.S. Pat. No. 3,832,579) and a method using an
electro-thermal conversion element (as shown in DE-OS 2843064).
In the above embodiment and the technical explanation, "drive frequency"
means a maximum drive frequency at which the liquid droplets are
discharged under a maximum condition, or a standard frequency for driving.
In accordance with the present invention, the head is driven at least one
drive frequency at which the stable discharge speed is independently
attained, in order to discharge the ink.
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